Allow clients to pass an initial_git_url of "empty", which creates a bare repo but does not add a commit.  When 'empty' is passed, the node will skip starting the gear and also skip the initial build.  This allows clients that want to send a local Git repository (one that isn't visible to OpenShift.com, for example) to avoid having to push/merge/delete the initial commit, and instead submit their own clean repo.  In this case, the user will get a result indicating that their repository is empty.

Also resolves 977985 by removing the message.